Indebtedness Interest expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Interest Expense, Long-term Debt	$ 109,842	$ 91,286	$ 62,683
interest expense to loan participant	110	2,430	2,295
interest expense credit facility	2,122	4,278	4,785
Interest Expense	111,964	95,564	67,468
Multifamily [Member]
Debt Instrument [Line Items]
Interest Expense, Long-term Debt	47,697	45,662	35,402
Retail Segment [Member]
Debt Instrument [Line Items]
Interest Expense, Long-term Debt	24,566	19,188	14,895
Office Building [Member]
Debt Instrument [Line Items]
Interest Expense, Long-term Debt	22,711	12,789	7,006
Interest Expense	22,869	12,789	7,006
Student Housing Communities [Member]
Debt Instrument [Line Items]
Interest Expense, Long-term Debt	$ 14,758	$ 11,217	$ 3,085